1. Field of the Invention
The present invention relates to a video signal processing apparatus that processes an input video signal to display at high quality on a display device, the input video signal being a telecine-converted video signal generated by the 2-3 pulldown conversion system, from a movie film.
2. Description of the Related Background Art
Video signals of a standard television format, such as the NTSC format, often include video signals based on films. A movie film has 24 film frames per second. A video signal of the standard television format has 30 frames per second, and is an interlaced scan video signal having two fields for each frame. Since the number of frames per second differs between a video signal and a movie film, each frame of the movie film is usually telecine-converted by the 2-3 pulldown conversion system to obtain a video signal of the standard television format.
In the 2-3 pulldown conversion system, the first and the second field of the first frame of a video signal are produced from the first film frame, the first and the second field of a second frame and a first field of a third frame of the video signal are produced from the second film frame, and the second field of the third frame and the first field of a fourth frame of the video signal are produced from the third film frame. The following frames are converted similarly, so that two fields, three fields, two fields, three fields, etc. of the video signal are respectively produced from each consecutive film frame.
Thus, two film frames correspond to five frames of a standard television format video signal, and each film frame is alternately converted into a video signal of two fields and a video signal of three fields.
However, when a video based on the interlaced scan video signal which is telecine-converted is displayed on a display device, such as a PDP, then, for example, the third frame of the consecutive frames of the video signal is combined from images of the second and the third frames of the movie film. Therefore, there was a problem that the image quality is poorer than that of an original movie film.
In order to overcome the above problem, Japanese Patent Laid-Open No. 2001-346131 discloses that a telecine-converted interlaced scanning video signal is converted by an interfiled interpolation process into a line sequential scanning video signal, which is thinned out and written in a memory on a field unit base, and that the line sequential scanning video signal written in a memory is repeatedly read out n times from the memory at a rate of n times (n denotes an integral number not lower than 2 as such 2) as high as 24 Hz.
As described above, two film frames of a film source correspond to five frames of a line sequential scanning video signal when the interlaced scanning video signal having 60 fields per second, which is telecine-converted by the 2-3 pulldown conversion system from the film source having 24 film frames per second, is further converted into the line sequential scanning video signal. In the line sequential scanning video signal, two-frame video signals per film frame and three-frame video signals per film frame are thus alternately repeated.
When the frame rate is changed from five frames (a 2-3 pattern) to six frames (a 3-3 pattern) of such video signal in conversion of two film frames of a film source, conversion into a 2-4 pattern occurs regardless of a changing point of a film frame of the film source, which causes a problem that the display quality deteriorates.